|Publication number||US5195587 A|
|Application number||US 07/846,372|
|Publication date||Mar 23, 1993|
|Filing date||Mar 4, 1992|
|Priority date||Mar 4, 1992|
|Also published as||CA2088876A1|
|Publication number||07846372, 846372, US 5195587 A, US 5195587A, US-A-5195587, US5195587 A, US5195587A|
|Inventors||Willis G. Webb|
|Original Assignee||Conoco Inc.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (10), Referenced by (35), Classifications (18), Legal Events (11)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This invention relates to a vapor recovery system and more particularly to a vapor recovery system for recovering vapors from storage tanks housing liquids containing some gaseous vapors.
This system was developed for use in an oil field production facility and would likely have use in other hydrocarbon process facilities having similar system characteristics as will be further discussed herein.
It is well known that storage tanks used for storing process liquids in oil field operations develop gaseous vapors in the upper portions of such tanks as gases come out of solution in process liquids. If these vapors occur in sufficient quantity to economically justify their recovery, it is often expedient to collect the vapors, pressurize them and pass them into a so called sales line for commercial disposal. On the other hand if such sales lines are not readily available or if the gases do not occur in sufficient quantity, it has been common in the past to vent such vapors to the atmosphere or to burn them in a flare.
More recently, with the advent of the Clean Air Act coupled with more rigid state and local air quality standards, some of these previous disposal methods are no longer viable. Past methods of vapor recovery on oilfield leases in particular have focused on commercial rather than environmental concerns. New air quality standards are expected to significantly increase the demand for systems that find ways to avoid disposing of storage tank vapors into the atmosphere either by direct venting or flaring. Tighter emission standards will demand better disposal systems which heretofore have been quiet costly. For some oilfield lease operators, the difference between shutting down a lease and keeping it pumping will depend on how economically vapor emissions can be controlled. In this regard a currently available system which is designed to decrease the cost of emission control involves a skid mounted gas collection and compression system for dealing with small amounts of gas from tanks in a typical production lease tank battery. However these systems require the use of a gas compressor which is relatively expensive to install and operate. For leases that are economically marginal, theses additional expenses may mean the economic end of some lease operations. These vapor recovery compressor units may require as many as four motors, one for running the compressor, one to pump lubricating oil into the compressor, one to operate a cooling system, and sometimes one to pump recovered liquid. Maintenance on compressors is fairly high due to its mechanical characteristics involving precision moving parts, high pressures, etc. Operating costs which include electrical power and lubricating oil are also relatively high.
It is therefore an object of the present invention to provide a new and improved vapor recovery system that meets the requirements of the Clean Air Act, which requires low capital expenditures, and has low maintenance and operating costs.
With these and other objects in view the present invention contemplates a system for collecting vapors from one or more vessels and feeding such vapors to a common line for recovery or disposal. A vapor detection device senses that vapors have reached a certain pressure level within the collection system and in response to such detection operates a valve to provide a supply of process fluids under pressure to a jet pump to act as a motive fluid for operating the jet pump. The collected vapors pass into a suction inlet on the jet pump and are then entrained into the process fluids driving the jet pump.
In a hydrocarbon production setting the gas entrained process fluids are recycled to a separator for initially separating production fluids before they are sent to the vessels from which the vapors are being taken. In such an oil field production system the process fluid will most likely be water under pressure from a water flood system or water being pumped from a water storage tank, with the pump being operated by the vapor detection device. If the process fluid is water, the gas entrained water may be disposed of such as by injection into underground formations.
FIG. 1 is a perspective view of portions of an oil field production facility showing the present invention; and
FIG. 2 is a cross sectional view of a jet pump for use the present invention.
Referring first to FIG. 1 a production lease includes flowlines 11 which extend from wells (not shown) to the process facility for bringing produced fluids from the wells on the lease to the facility. The produced fluids from the wells are fed into a manifold 13 from which they are transferred by a line 15 to a primary separation device 17. There are any number of separation schemes which would be used at this point in a production separation process, with most schemes being more complex than a single separation vessel. However for purposes of illustration the single vessel shown in FIG. 1 is intended to represent such a function in the scheme of this invention. The ultimate purpose of such separation systems is to usually remove most of the free gas from the production stream and to separate oil and water in the production stream. Sufficient pressure is usually maintained in the effluent from the separator to move these fluids to storage tanks. The effluent streams from the separator 17 could of course be pumped to the tanks. FIG. 1 shows an oil leg from the separator passing oil by way of flowline 21 to oil storage tank 27. Likewise a water leg is passed through flowline 23 to water storage tank 25. Of course it is common that a larger number of tanks are involved in such a facility than shown in FIG. 1 and that water tanks may predominate because of a predominance of water in the production stream. Gas is shown being taken from the separator 17 by means of line 19 for disposal to sales or the like.
Vent lines 29 and 31 are shown rising from the top of water tank 25 and oil tank 27 respectively. These vent lines connect to a common vapor gathering line 33. One end of line 33 is shown connecting to a motor valve 35 which would control output to a flare or otherwise provide for emergency disposal in the present system. The other end of vapor gathering line 33 connects with jet pump or ejector 43.
Ejector 43 is supplied with a motive fluid by means of flowline 41 which in turn is connected to a supply of pressured fluid such as process water. A typical scheme in such a production lease would use waterflood process water under a system pressure of say 200 psi to act as the motive fluid to operate the pump 43. A motor valve 39 is shown positioned in line 41 which would supply this water under pressure. A vapor detection and control device 37 is shown connected by means of a line 38 to a vapor space in one of the tanks in order to detect the common vapor pressure of the system, since the line 33 is at a common pressure with vapors in all the tanks. When the vapor pressure in this common system reaches a certain level, a switch in the control system is activated which in turn sends electrical power or a control signal to motor valve 39. Dotted line 40 represents a path for the control signal. In the present example this control device was an apparatus sold by UMC Automation of Midland Texas termed "Vapor Recovery Control, E-Z Controller".
An alternative water supply source is shown as flowline 51 (dotted line) from the water tank 25 to provide a source of water to pump 53 which in turn would supply pressured water through pump output line 55 to line 41 and thus to ejector 43. Dotted line 42 represents a path for the control signal from control device 37 to operate pump 53.
A suction strainer 47 is provided upstream of the pump 43 for cleaning debris from the line. A check valve 49 is shown in the discharge line 45 from ejector 43 to isolate the vapor system in line 33 when the pump 43 is not being operated. Line 45 passes the fluids emerging from pump 43 back to the inlet line 15 to the separator 17.
Referring to FIG. 2, the jet pump or ejector 43 is shown having an inlet 59 which passes motive fluid through a nozzle 65 into a suction chamber 61.
Suction chamber 61 is connected with a suction inlet 63. Motive fluid passes through chamber 61 into a parallel section 62 and then into a diffuser section 64 which outlets fluids from the pump through outlet 71.
In the operation of such an ejector, the pumping or motive fluid enters an inlet 59 and passes through a venturi nozzle 65 which is centered in the flowstream. As it passes through the venturi nozzle, a suction is developed that causes fluids in the suction chamber 61 to be entrained into the pumping fluid. The suction inlet delivers fluid to be pumped to the suction chamber 61. In the present case, gas vapors are supplied by means of line 33 to the suction inlet where such vapors are delivered to the suction chamber 61 for entrainment into the motive stream which is water in this example.
The performance of an ejector is a function of the area of the motive fluid nozzle and venturi throat, pressure of motive fluid, suction and discharge pressures, as well as physical characteristics of the fluids involved. In the present example a Penberthy Jet Pump Model 11/2 ELL Exhauster was used satisfactorily using pumping water supplied at 200 psi. These jet pumps operate on the principle of a operating fluid entraining a second fluid. The operating fluid (water in this instance) under pressure enters the inlet and travels through the nozzle into the suction chamber. The nozzle converts the pressure of the operating medium into a high velocity stream which passes from the discharge side of the inlet nozzle. Pumping action begins when vapors in the suction chamber are entrained by the high velocity stream emerging from the nozzle, lowering the pressure in the suction chamber. This causes the vapor in the suction chamber to flow toward the discharge thus mixing or entraining the material in the suction chamber with the operating fluid when it acquires the energy of the operating fluid in the parallel section. In the diffuser section, part of the velocity of the mixture is converted to a pressure greater than the suction pressure but lower than the operating medium pressure. In the present example, this exit pressure is approximately 20 psi.
In the operation of the system described in FIGS. 1 and 2, production fluids are collected from a number of producing wells through production flowlines 11 where they are then merged in manifold 13 and passed into a separator 17. This separator is typically a three phase system that liberates gas from the production fluids for disposal to gas sales by means of line 19. Oil and water streams from separator 17 are passed to storage tank 27 and 25 respectively for further disposal. This water may be then utilized in a water flood operation as the motive fluid. Alternatively the water may simply be reinjected into an underground formation for disposal or otherwise disposed of. The oil in storage tank 27 would normally be passed to sales such as by pipeline or trucking. The oil and water components of the produced fluids in tanks 25, 27 have gases in solution which will come out of solution in the storage tanks and collect at the top of the tanks. These hydrocarbon vapors ca contain toxic substances and therefore it may be hazardous to simply vent these vapors to the atmosphere. Flaring theses gases may likewise be environmentally undesirable. In the present system these vapors are passed by vent lines 29, 31 at the tops of tanks 25, 27; into vapor collection line 33 which is at a substantially common pressure with the vapor pressure in each of the tanks. This common vent line 33 communicates these vapors with the suction inlet 63 on the ejector 43. When the vapor pressure in the tanks and collection line reaches a certain predetermined level, this predetermined pressure level is communicated by line 38 to the vapor recovery control 37 where it causes activation of control valve 39 or pump 53 to provide a supply of motive fluid to the ejector 43. This passage of motive fluid under pressure through ejector 43 causes entrainment of vapors from line 33 into the motive fluid, which is water in this instance. This water and entrained gas is recycled to separator 17 where it again is separated into its constituent phases. Some of the entrained gases will be passed through line 19 to gas sales and typically some of the entrained vapors (gas) will pass in solution with the water and oil components of the fluid mixture passing through the separator. Some of these gas vapors will then pass back to the storage tanks where again they will pass through the process cycle just described. In this way a portion of the vapors from the tanks will pass to gas sales to provide for economic recovery of these gas components. An alternative flow scheme is characterized by passing the gas entrained water from the ejector into a reinjection system for injecting these fluids into an underground formation.
The low cost associated with the jet ejector system just described will now make it possible to economically deal with the vapor emissions which are associated with such petroleum production operations.
While this invention has been described in relation to a particular petroleum production scheme, it is appreciated that there may be many industrial applications where fugitive vapors are in need of safe disposal and where costs of dealing with the situation are prohibitive.
Therefore while particular embodiments of the present invention have been shown and described, it is apparent that changes and modifications may be made without departing from this invention in its broader aspects, and therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention.
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|U.S. Classification||166/267, 166/268, 137/172, 210/143, 210/258, 137/173, 210/539, 210/188, 210/521, 166/53|
|International Classification||E21B43/34, E21B43/40|
|Cooperative Classification||E21B43/34, E21B43/40, Y10T137/3009, Y10T137/3006|
|European Classification||E21B43/40, E21B43/34|
|Mar 4, 1992||AS||Assignment|
Owner name: CONOCO INC. A CORP. OF DELAWARE, OKLAHOMA
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:WEBB, WILLIS G.;REEL/FRAME:006061/0890
Effective date: 19920302
|Oct 29, 1996||REMI||Maintenance fee reminder mailed|
|Feb 25, 1997||AS||Assignment|
Owner name: SEPCO INDUSTRIES, INC., TEXAS
Free format text: MERGER;ASSIGNOR:SOUTHERN ENGINE AND PUMP COMPANY;REEL/FRAME:008366/0387
Effective date: 19940301
|Feb 26, 1997||FPAY||Fee payment|
Year of fee payment: 4
|Feb 26, 1997||SULP||Surcharge for late payment|
|Oct 17, 2000||REMI||Maintenance fee reminder mailed|
|Dec 12, 2000||FPAY||Fee payment|
Year of fee payment: 8
|Dec 12, 2000||SULP||Surcharge for late payment|
Year of fee payment: 7
|Sep 22, 2004||FPAY||Fee payment|
Year of fee payment: 12
|May 11, 2012||AS||Assignment|
Owner name: JPMORGAN CHASE BANK, N.A., AS COLLATERAL AGENT, NE
Free format text: SECURITY INTEREST;ASSIGNOR:RBC EUROPE LIMITED, AS EXISTING ADMINISTRATION AGENT AND COLLATERAL AGENT;REEL/FRAME:028198/0285
Effective date: 20120510
|Jul 27, 2012||AS||Assignment|
Owner name: WELLS FARGO BANK, NATIONAL ASSOCIATION, AS ADMINIS
Free format text: NOTICE OF GRANT OF SECURITY INTEREST IN PATENTS;ASSIGNOR:DXP ENTERPRISES, INC.;REEL/FRAME:028655/0026
Effective date: 20120711